Some sensor devices such as a flowmeter and a thermo-hygrometer use a wireless communication function by radio waves instead of conventional wired connection for cost reduction with less wiring use and for monitoring and controlling from a remote place (see Patent Literature 1, for example). FIG. 8 is a block diagram illustrating a conventional wireless measurement system using such a wireless communication function. A typical wireless measurement system includes an information processing device 101 as a parent node such as a relay node or a gateway node and wireless communication devices 102 as end leaf nodes (child nodes). Data that is wireless-transmitted from the wireless communication devices 102 is stored in a database 103 via the information processing device 101.
The wireless communication devices 102 are nodes at ends of a network, and perform communication less frequently than the information processing device 101. Therefore, the wireless communication devices 102 have a feature of consuming less amount of electrical power than the information processing device 101. Further, the wireless measurement device requires removing not only a signal line but also a feeder line. Therefore the wireless communication device 102 often uses a battery as its power source. FIG. 9 illustrates specific examples of the wireless communication device 102. Example in FIG. 9A shows a sensor 104 and a battery-type wireless communication device 102a that are separately provided. Example in FIG. 9B shows a sensor-integrated battery type wireless communication device 102b including a sensor therein. In this way, the wireless communication device 102 often uses a battery as its power source. Accordingly, the wireless communication device 102 has a restriction on the operable time.